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Groups > comp.lang.c > #138642

Re: Big integers

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.lang.c
Subject Re: Big integers
Date 2018-12-10 15:27 +0100
Organization A noiseless patient Spider
Message-ID <pult4s$bpf$1@dont-email.me> (permalink)
References (2 earlier) <pugjht$pja$1@dont-email.me> <pugjm7$pja$2@dont-email.me> <iRQOD.253903$2T2.61156@fx42.am4> <b0ede079-5f28-4f16-9423-9e2223f6fbb0@googlegroups.com> <a0c099dc-d140-43ab-999f-f331bf45e0a3@googlegroups.com>

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On 10/12/18 14:22, Malcolm McLean wrote:
> On Monday, December 10, 2018 at 1:10:43 PM UTC, Thiago Adams wrote:
>> On Saturday, December 8, 2018 at 12:48:53 PM UTC-2, Bart wrote:
>> ...
>>> The new library will do some of that, as it's for floating point and 
>>> needs a few extra bits. 
>>
>> Who needs bigreal? I don't know any usage.
>>
>> To do math what is necessary is symbolic math. At the 
>> end you can ask the answer in a numeric form and then
>> you can compute using more and more decimal places. Just
>> at the end and not during the computation. So I don't any
>> application for big float points. Maybe a fixed 128 and thats it.

I too am curious about the applications.  This is not really my field,
and I am interested to hear about use-cases.

For very large integer stuff, I know of two main types of use.  One is
for encryption work.  In those cases, you generally have a fixed known
size for the numbers you are using - that would allow you some
conveniences compared to dynamic sizing, but I expect the efficiency
gains would be fairly small in practice.

The other use is in number theory mathematics, combinatorics, etc.

For floating point, quad precision (128-bit) is available in hardware on
a couple of devices, and octal precision is defined as an IEEE format.
I expect that for some kinds of numerical calculation, more than double
precision can be useful - such as for working with large matrices or
polynomials where you can often be mixing values over a very large
dynamic range.

But I don't know of any uses of arbitrary precision floating point data,
except perhaps for some mathematical curiosities.  And of course, there
is the fun of writing such libraries!

>>
> Big reals are useful in graphics algorithms for resolving the degenerate/
> near degenerate problem. For example you are asked to solve the intersection
> of two lines which share an endpoint calculated in two mathematically
> equivalent ways, but with slightly different floating point results.
> 

Graphics algorithms are more likely to use very short types, not very
long ones.

And the intersection of two lines which share an endpoint is that
endpoint (unless the lines are coincident).

So I think you'll have to explain that one a little better if it is to
make sense.

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Big integers Bart <bc@freeuk.com> - 2018-12-04 12:17 +0000
  Re: Big integers fir <profesor.fir@gmail.com> - 2018-12-04 05:58 -0800
    Re: Big integers Chad <cdalten@gmail.com> - 2018-12-04 08:22 -0800
      Re: Big integers Bart <bc@freeuk.com> - 2018-12-04 17:04 +0000
        Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-04 17:19 +0000
  Re: Big integers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-04 08:38 -0800
    Re: Big integers Bart <bc@freeuk.com> - 2018-12-04 17:35 +0000
      Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-04 18:13 +0000
        Re: Big integers "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-04 10:50 -0800
        Re: Big integers Rosario19 <Ros@invalid.invalid> - 2018-12-06 17:56 +0100
      Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-04 10:22 -0800
        Re: Big integers Eli the Bearded <*@eli.users.panix.com> - 2018-12-04 18:58 +0000
          Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-04 11:32 -0800
            Re: Big integers Eli the Bearded <*@eli.users.panix.com> - 2018-12-04 22:45 +0000
              Re: Big integers jameskuyper@alumni.caltech.edu - 2018-12-04 14:57 -0800
          Re: Big integers jameskuyper@alumni.caltech.edu - 2018-12-04 12:14 -0800
          Re: Big integers chris.m.thomasson.1@gmail.com - 2018-12-04 16:58 -0800
            Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 03:14 +0000
              Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 14:27 -0800
            Re: Big integers Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-04 20:03 -0500
              Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 14:25 -0800
      Re: Big integers jacob navia <jacob@jacob.remcomp.fr> - 2018-12-04 23:45 +0100
        Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-04 23:29 +0000
        Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 00:30 +0000
          Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 14:28 -0800
        Re: Big integers Jens Stuckelberger <Jens_Stuckelberger@nowhere.net> - 2018-12-05 17:50 +0000
          Re: Big integers jacobnavia <jacob@jacob.remcomp.fr> - 2018-12-05 20:03 +0100
        Re: Big integers Keith Thompson <kst-u@mib.org> - 2018-12-05 13:46 -0800
          Re: Big integers jacobnavia <jacob@jacob.remcomp.fr> - 2018-12-06 06:41 +0100
            Re: Big integers Keith Thompson <kst-u@mib.org> - 2018-12-05 22:40 -0800
  Re: Big integers "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-04 09:08 -0800
    Re: Big integers Bart <bc@freeuk.com> - 2018-12-04 19:41 +0000
      Re: Big integers "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-04 12:00 -0800
    Re: Big integers Bart <bc@freeuk.com> - 2018-12-08 11:28 +0000
  Re: Big integers Ian Collins <ian-news@hotmail.com> - 2018-12-05 15:19 +1300
    Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 11:58 +0000
      Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-05 14:35 +0100
        Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 14:35 +0000
          Re: Big integers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-05 07:39 -0800
            Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-05 07:45 -0800
              Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 17:51 +0000
                Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-05 22:19 +0100
              Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 14:55 -0800
                Re: Big integers jameskuyper@alumni.caltech.edu - 2018-12-05 15:19 -0800
                Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 16:13 -0800
                Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-06 09:35 +0100
                Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-07 14:26 -0800
                Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-07 19:56 -0800
                Re: Big integers James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-09 12:01 -0500
                Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-10 14:47 -0800
                Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 00:50 +0000
                Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-10 17:37 -0800
                Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-14 21:18 -0800
          Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-05 07:57 -0800
          Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 15:59 +0000
            Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 22:59 +0000
              Re: Big integers jameskuyper@alumni.caltech.edu - 2018-12-05 15:31 -0800
                Re: Big integers Robert Wessel <robertwessel2@yahoo.com> - 2018-12-05 20:03 -0600
              Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-05 23:42 +0000
                Re: Big integers James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-05 20:15 -0500
              Re: Big integers Ike Naar <ike@iceland.freeshell.org> - 2018-12-10 07:26 +0000
                Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 18:38 +0000
                Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-10 19:10 +0000
                Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 21:23 +0000
                Re: Big integers Ike Naar <ike@iceland.freeshell.org> - 2018-12-10 22:47 +0000
          Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-05 22:15 +0100
        Re: Big integers Bart <bc@freeuk.com> - 2018-12-06 13:43 +0000
          Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-06 07:50 -0800
      Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 15:19 +0000
        Re: Big integers luser droog <luser.droog@gmail.com> - 2018-12-10 23:19 -0800
          Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-11 08:45 +0100
            Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-11 11:15 +0000
              Re: Big integers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-11 04:36 -0800
                Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-11 14:35 +0100
              Re: Modules again (was: Big integers) Bart <bc@freeuk.com> - 2018-12-11 12:53 +0000
                Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 14:45 +0100
                Re: Modules again Bart <bc@freeuk.com> - 2018-12-11 16:08 +0000
                Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 21:37 +0100
                Re: Modules again Thiago Adams <thiago.adams@gmail.com> - 2018-12-11 08:59 -0800
                Re: Modules again Bart <bc@freeuk.com> - 2018-12-11 17:49 +0000
                Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 21:44 +0100
                Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 18:02 +0000
                Re: Modules again Thiago Adams <thiago.adams@gmail.com> - 2018-12-11 10:10 -0800
                Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 18:54 +0000
                Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-11 13:14 -0500
                Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 18:54 +0000
                Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-11 14:42 -0500
                Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 21:54 +0100
                Re: Modules again Keith Thompson <kst-u@mib.org> - 2018-12-11 14:53 -0800
                Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-12 08:24 +0100
                Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 21:51 +0100
                Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 23:24 +0000
                Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-11 18:44 -0500
                Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-11 18:45 -0500
                Re: Modules again Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-12-12 06:39 +0000
                Re: Modules again James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-12 07:59 -0500
                Re: Modules again mark.bluemel@gmail.com - 2018-12-12 05:43 -0800
                Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-12 14:20 +0000
                Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-12 17:10 +0100
                Re: Modules again James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-12 13:39 -0800
                Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-12 14:19 +0000
                Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-12 10:28 -0500
      Re: Big integers Ian Collins <ian-news@hotmail.com> - 2018-12-06 08:10 +1300
        Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 20:57 +0000
          Re: Big integers Ian Collins <ian-news@hotmail.com> - 2018-12-06 10:16 +1300
            Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 23:15 +0000
              Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-05 23:44 +0000
  Re: Big integers Robert Wessel <robertwessel2@yahoo.com> - 2018-12-05 02:51 -0600
  Re: Big integers antispam@math.uni.wroc.pl - 2018-12-07 15:26 +0000
    Re: Big integers Bart <bc@freeuk.com> - 2018-12-07 16:27 +0000
      Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-07 16:36 +0000
        Re: Big integers Bart <bc@freeuk.com> - 2018-12-07 17:01 +0000
      Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-07 17:55 +0000
      Re: Big integers antispam@math.uni.wroc.pl - 2018-12-07 19:26 +0000
        Re: Big integers Bart <bc@freeuk.com> - 2018-12-07 21:39 +0000
          Re: Big integers Ian Collins <ian-news@hotmail.com> - 2018-12-08 10:51 +1300
  Re: Big integers Anton Shepelev <anton.txt@gmail.com> - 2018-12-08 00:43 +0300
    Re: Big integers Bart <bc@freeuk.com> - 2018-12-08 01:08 +0000
    Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-08 15:13 +0100
      Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-08 15:15 +0100
        Re: Big integers Bart <bc@freeuk.com> - 2018-12-08 14:48 +0000
          Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-10 05:10 -0800
            Re: Big integers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-10 05:22 -0800
              Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-10 15:27 +0100
                Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-10 15:59 +0000
                Re: Big integers antispam@math.uni.wroc.pl - 2018-12-11 21:14 +0000
            Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 14:56 +0000
              Re: Big integers Ike Naar <ike@iceland.freeshell.org> - 2018-12-10 17:46 +0000
                Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 18:24 +0000
                Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-10 11:12 -0800
                Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-10 11:23 -0800
                Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 21:44 +0000
                Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-11 10:20 -0800
                Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-11 13:15 -0800
      Re: Big integers Keith Thompson <kst-u@mib.org> - 2018-12-08 12:14 -0800
        Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-09 13:31 +0100
      Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-08 15:52 -0800
  Re: Big integers Bart <bc@freeuk.com> - 2018-12-16 19:29 +0000
  Re: Big integers "Tristan B. Kildaire" <deavmi@disroot.org> - 2018-12-25 12:59 +0000
    Re: Big integers Bart <bc@freeuk.com> - 2018-12-25 15:54 +0000

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